Certain diagnostic and therapeutic procedures require access to and/or formation of a cavity in an interior body region. These procedures can be used to treat cortical bone which, due to osteoporosis, avascular necrosis, cancer, or trauma, for example, may be fractured or prone to compression/collapse. Spinal compression fractures and related spinal deformities, if not successfully treated, can lead to deformation of the normal alignment or curvature, e.g., lordosis, of the affected area of the spine, as well as chronic complications and an overall adverse impact upon the quality of life for the patient. Until recently, doctors were limited to treating such compression fractures and related deformities with pain medications, bed rest, bracing or invasive spinal surgery.
More recently, minimally invasive surgical procedures for treating vertebral compression fractures have been developed. These procedures generally involve the insertion of a rigid cannula, needle or trocar into the interior of a collapsed or otherwise damaged vertebra. The cannula usually includes a lumen or central passage through which another tool, implant or filler material is passed in order to reposition and/or augment the vertebral body.
The most basic of these procedures is vertebroplasty. Vertebroplasty involves injecting a medical-grade bone cement (such as polymethylmethacrylate, a.k.a., PMMA) via a special bone needle into a fractured vertebra. The bone cement is injected with sufficient pressure to compress and displace cancellous bone tissue. However, the direction and containment of the injected cement can be difficult to control because the space the bone cement occupies is ill-defined, self-forming, and highly-dependent upon the internal composition of the cancellous bone. Additionally, vertebroplasty does not always reposition the fractured bone and therefore may not address the problem of spinal deformity due to fracture.
A number of more advanced treatments for vertebral compression fractures are known, and generally involve two phases: (1) reposition, or restoration of the original height of the vertebral body and consequent lordotic correction of the spinal curvature; and (2) augmentation, or addition of material to support or strengthen the fractured bone. As with vertebroplasty, such procedures generally involve use of a cannula, catheter, needle, trocar or other introducer to provide access to the interior of the effected vertebral body.
Procedures, such as kyphoplasty, provide better bounding and control over injected bone cement, other procedures utilize devices for first forming cavities within the cancellous bone (and, accordingly, other interior body regions) prior to injecting bone cement into such a cavity. During balloon kyphoplasty (Kyphon, Inc.), an expandable body or balloon is deployed into the interior body region to form a cavity in, for example, cancellous bone tissue surrounded by fractured cortical bone. Kyphoplasty then achieves the reconstruction of the lordosis, or normal curvature, by inflating the balloon, which expands within the vertebral body restoring it to its original height. These expandable body devices effectively compress and displace the cancellous bone to form an interior cavity that then receives a filling material intended to provide renewed interior structural support for cortical bone.
A common drawback of most systems for repositioning and augmenting damaged vertebrae is that they involve the use of relatively complex apparatus introduced through rigid introducers. These introducers provide little tactile feedback and directional control to the surgeon. Accordingly, there remains a need in the art to provide safe and effective apparatus and methods for minimally invasive repositioning of and osteopathic augmentation of vertebral bodies to restore lordosis of the spine.